如图反映的是地球上七大洲的面积占陆地总面积的百分比，小明根据如图得出了

下列四个结论：

①七大洲中面积最大的是亚洲；

②南美洲、北美洲、非洲三大洲的面积和约占陆地总面积的50%；

③非洲约占陆地总面积的20%；

④南美洲的面积是大洋洲面积的2倍．

你认为上述四个结论中正确的应该是（　　）

下列关于生态系统的信息传递的叙述中，正确的是(    )

根据句义完成句中已给出首字母的单词。将每个完整的单词写在各小题右边的横线上
 Don't  w____ about your dog. I believe it can find the way back.
 My sister will take her f____  examination next week, and then she will leave university.
You have left dirty m____  on the door. Clean them up.
The teacher often asks the students to keep away from the s____  they meet.
You should leave i____ . The bus is leaving soon.